The use of high viscosity low cost fuels, such as residual petroleum fuels, in internal combustion engines is presently limited to very large bore, slow speed, marine diesel engines. In these large bore engines, the high fuel injection pressures, needed for adequate atomization of residual petroleum fuels, can be utilized without excessive fuel penetration and cylinder wall impact, since the large cylinder diameter provides an adequately long fuel spray penetration path. But in medium speed, medium bore, diesel engines, and particularly in high speed, small bore, diesel engines, these high viscosity residual petroleum fuels are poorly burned. Either poor atomization results, at injection pressures low enough to avoid fuel impact on the cylinder wall, or fuel impact on the cylinder wall occurs, at the high injection pressures needed for adequate atomization of these high viscosity fuels.
Preatomizing the fuel, outside of the engine cylinder volume, and suspending the very small fuel particles in a continuous water phase, to create a fuel-in-water slurry offers a potential method for utilizing high viscosity residual petroleum fuels, in both medium bore, medium speed, diesel engines, and small bore, high speed, diesel engines, which are widely used in our transportation systems. An example method and apparatus for preparing such residual petroleum fuel in water slurries is described in U.S. Pat. No. 6,444,000, 2002, Firey. Use of such preatomized, fuel in water slurries would appear to relieve the engine fuel injection system of the obligation to carry out the full extent of atomization needed for rapid and complete fuel burning, and hence the lower fuel injection pressures, with the reduced penetration, needed in small or medium bore engines can be used, and yet adequate atomization, with rapid and complete fuel combustion, will result.
Engine experiments, with coal particle in water slurry fuels, in medium speed, medium bore, railroad diesel engines, revealed a potential limitation in the combustion benefits to be obtained by use of increasingly smaller fuel particle size, in fuel in water slurry fuels. As fuel particle size was reduced, the effective viscosity of the slurry increased, and larger slurry droplet size resulted when the slurry was injected into the engine cylinder volume. Thus a greater number and weight of fuel particles resided within each injected slurry droplet, as fuel particle size was reduced.
Indications are that within each slurry droplet, the several separate small fuel particles tended to reagglomerate into one, or a few, larger fuel particles, when the water phase evaporated prior to ignition and combustion. The result was that, the benefits sought by preatomizing the fuel into smaller particles, were not realized, and best engine results were obtained at intermediate fuel particle size.
The capability of operating a major portion of our transportation system on low cost residual petroleum fuels, instead of the present high cost distillate petroleum fuels, would be a substantial benefit. Diesel engine operators would realize a reduced fuel cost. The national effort toward energy independence would be promoted, since the stationary energy applications, currently using residual fuels, could more readily and economically shift to coal use than is possible for the critical transportation sector.
None of the apparatus drawings are to scale.